Fire kills people and destroys property. Any material that offers flame retardance benefits the public. Flame retardants are often added to compounds to provide flame resistance to products made from such compounds.
Nanoclays are exciting additives for a variety of purposes, including flame retardancy. U.S. Pat. Nos. 6,376,591; 6,251,980; 6,232,388; 6,225,394; 6,090,734; 6,050,509; 5,998,528; 5,844,032; and 5,837,763 disclose the manufacture and use of nanocomposites. Nanocor, Inc. is a significant commercial source of exfoliated or intercalated nanoclays and has a web site: www.nanocor.com.
ASTM International (www.astm.org) has established a strict standard for testing the surface burning characteristics of building materials. This test is No. E84 and concerns the fire-test-response standard for the comparative surface burning behavior of building materials applicable to exposed surfaces such as walls and ceilings. The test is conducted with the specimen in the ceiling position with the surface to be evaluated exposed face down to the ignition source. To satisfy E84, the material, product, or assembly shall be capable of being mounted in the test position during the test. Thus, the specimen shall either be self-supporting by its own structural quality, held in place by added supports along the test surface, or secured from the back side.
There are other flame tests, such as MVSS-302 promulgated by the National Highway Transportation Safety Administration of the U.S. government. However, the E84 test is more stringent in performance because it concerns occupied buildings, not vehicles.
U.S. Pat. No. 6,414,070 (Kausch et al.) disclosed flame retardant polyolefin compounds that have passed the MVSS-302 test, in which the nanoclay is a required flame retardant and an inorganic flame retardant is optional.
PCT Patent Publications WO 00/66657 and WO 00/68312 both disclose thermoplastic materials containing both nanoclay and inorganic flame retardants.
None of these three documents report the ability of the compositions disclosed therein to pass the stringent ASTM E84 test.